The present invention relates to a mounting structure for one or more semiconductor devices, and more particularly to a mounting structure for one or more semiconductor devices allowing packaging in substantially the same size as the semiconductor device or devices and multi-pin mounting in high density.
A conventional semiconductor device mounting structure is disclosed in Japanese Patent Application Laid-open No. Hei 4-154136.
The mounting structure for semiconductor devices described in the Japanese Patent Application has a film carrier interposed between a bare chip and a substrate. The basic material of the film carrier is either a ceramic, such as alumina or aluminum nitride, or an organic material, such as polyimide or Teflon. On the upper surface of the film carrier are arranged pads for connection to the electrodes of flip chips, and on its lower surface are pads for connection to the electrodes of the substrate. Junctions between the flip chips and the film carrier may be Au (gold) to Au junctions, Au to Sn (tin) junctions or the like, and the film carrier and the substrate are soldered to each other.
Generally, where a semiconductor package mounted with a bare chip is to be mounted on a wiring board, it is necessary to match the thermal expansion coefficient of the semiconductor package itself and that of the wiring board, or where the difference in thermal expansion coefficient between the two is significant, it is necessary to disperse the stress in the junction and improve the reliability of connection by sealing in an under-filling material or the like.
However, the prior art referred to above takes no account of the thermal expansion coefficients of the bare chip and the film carrier. In order to secure the connection reliability of the junction between the bare chip and the film carrier, the basic material of the film carrier should preferably be aluminum nitride, whose thermal expansion coefficient is close to that of silicon (Si) chips, but the use of this material would give rise to the problem of a difference in thermal expansion coefficient between aluminum nitride and the wiring board and, if the film carrier is mounted on a printed circuit board having a high thermal expansion coefficient, a problem would arise as to the reliability of connection between the film substrate and the printed circuit board.
Where a bare chip is to be directly mounted on a printed circuit board, it is also common to seal in an under-filling material between the bare chip and the printed circuit board to ensure the connection reliability of the junction, but in the event of serious enough trouble with the bare chip to necessitate its replacement, the fixation with the under-filling material makes it prohibitively difficult to replace the bare chip.
An object of the present invention is to provide a mounting structure for one or more semiconductor devices, of which the external contour of the package is substantially as large as that of the integrated circuit chip, and which permits multi-pin connection and high-density packaging.
Another object of the invention is to provide a mounting structure for one or more semiconductor devices using a printed circuit board, which is inexpensive as a substrate on which to mount a semiconductor device and compatible with a large size.
Still another object of the invention is to provide a mounting structure permitting ready replacement of a defective or broken-down semiconductor device.